where \(\mu _{k,p}={\eta _k}(1 + {\rho _{k,p}^\star })\)  holds. Notice that the reformulated subproblem \({\cal P}_{ \rm active}\)  in (REF ) is still too difficult to solve due to the complexity of matrix inversion in \(f_{k,p}\)  in (REF ). Actually, this subproblem is a multi-variable sum-of-ratios problem, which has been discussed in [1]}. Inspired by the methods proposed in [1]}, here we can utilize the multidimensional complex quadratic transform to reformulate this subproblem, and then we obtain Proposition 2 as below.
